MadSci Network: Biochemistry
Query:

Re: Physiological and medical effects of l-stereoisomeric sugar

Date: Tue Aug 10 16:30:26 2010
Posted By: Billy Carver, Grad student, Biomedical Sciences, Vanderbilt University
Area of science: Biochemistry
ID: 1281201662.Bc
Message:

Hi Matthew,

Thanks for your question! http://upload.wikimedia.org/wikipedia/commons/a/ae/Sucralose2.svg

As a diabetic I consume a ton of sucralose (Splenda) without ever having thought too much about how it affects our bodies. Let’s start by describing what sucralose is. Sucralose is a chlorinated version of sucrose, or common table sugar [See the image to the right -- SM, Mod]. By replacing three hydroxyl (-OH) groups with chlorine atoms, the molecule is rendered unrecognizable by enzymes that degrade sucrose for our digestion. Because normal sugar-degrading enzymes cannot degrade it, no caloric energy can be derived from sucralose. Sucralose is not, however, a stereoisomer of sucrose. The chlorination process changes the chemical formula of sucrose to sucralose.

Sucralose primarily moves through the digestive system and is excreted in feces.

Research has shown that between 70% and 90% of radioactively labeled sucralose (imagine putting that in your coffee!) is excreted this way within five days of sucralose ingestion. In the same study, up to 15% of sucralose was excreted in urine -- almost all of it within 24 hours of administration. Radioactivity was also found in plasma after eating sucralose, but was quickly lost to urinary secretion. When sucralose is injected in rats, almost 80% of the compound is eliminated through the kidneys, with the rest excreted through the digestive tract. Because sucralose is excreted so quickly from the bloodstream, and because it does not interact with glucose oxidase, an enzyme used in most blood glucose testing kits, it would not influence blood sugar directly (I have to admit that I do not know if it would be identified as a carbohydrate by simpler tests such as iodine staining).
[The moderator adds: As explained in this answer (1055390550.Bc), iodine stains starch due to the physical structure of starch molecules; sucralose, being derived from a disaccharide, will not react with iodine. In addition, it seems unlikely that it will react with Benedict's solution, given that sucrose is not a reducing sugar (see (875669443.Bc). - - SM]

Interestingly, the poor absorption of sucralose through classic pathways in the digestive tract (endocytosis and active transport), along with its resistance to bacterial degradation, make sucralose a “splendid” tool for determining permeability of the digestive tract.

Many disease states cause the lining of the digestive system to become too permeable to many molecules. Without the ability to control the movement of solutes across the cells lining the digestive tract, undesirable molecules can enter the blood stream and valuable nutrients can be lost. Classically, sugars that cannot be digested by our bodies were administered to patients and their urine was checked for these sugars. The problem is that once those indigestible sugars reached the colon, bacteria residing there would digest it themselves and it would no longer be indigestible. Sucralose is totally invulnerable to bacteria living in our bodies, so doctors can administer sucralose and check urine for its presence. The amount present in the urine can help determine the health of our digestive systems.

I hope this answers your question!

Thanks!

Billy Carver.

A Anderson, P Poon, G Greenway, and J MacFie. “A simple method for the analysis of urinary sucralose for use in tests of intestinal permeability.” Ann Clin Biochem 2005; 42: 224-226.

J Sims, A Roberts, J Daniel, and A Renwick. “The metablic fate of sucralose in rats.” Food and Chemical Toxicology 2000;38(S2): 115-121.

A Roberts, A Renwick, J Sims, and D Snodin. “Sucralose Metabolism and Pharmacokinetics in Man.” Food and Chemical Toxicology 2000; 38(S2): 31-41.


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